Establishment and characterization of a fucosylated α-fetoprotein-specific monoclonal antibody: a potential application for clinical research

Highly sensitive two-dimensional profiling of N-linked glycans by hydrophilic interaction liquid chromatography and dual stacking capillary gel electrophoresis

BACKGROUND

N-Glycosylation is one of the most important post-translational modifications in proteins. As the N-glycan profiles in biological samples are diverse and change according to the pathological condition, various profiling methods have been developed, such as liquid chromatography (LC), capillary electrophoresis (CE), and mass spectrometry. However, conventional analytical methods have limitations in sensitivity and/or resolution, hindering the discovery of minor but specific N-glycans that are important both in the basic glycobiology research and in the medical application as biomarkers. Therefore, a highly sensitive and high-resolution N-glycan profiling method is required.

RESULTS

In this study, we developed a novel two-dimensional (2D) separation system, which couples hydrophilic interaction liquid chromatography (HILIC) with capillary gel electrophoresis (CGE) via large-volume dual preconcentration by isotachophoresis and stacking (LDIS). Owing to the efficient preconcentration efficiency of LDIS, limit of detection reached 12 pM (60 amol, S/N = 3) with good calibration curve linearity (R2 > 0.999) in the 2D analysis of maltoheptaose. Finally, 2D profiling of N-glycans obtained from standard glycoproteins and cell lysates were demonstrated. High-resolution 2D profiles were successfully obtained by data alignment using triple internal standards. N-glycans were well distributed on the HILIC/CGE 2D plane based on the glycan size, number of sialic acids, linkage type, and so on. As a result, specific minor glycans were successfully identified in HepG2 and HeLa cell lysates.

SIGNIFICANCE AND NOVELTY

In conclusion, the HILIC/CGE 2D analysis method showed sufficient sensitivity and resolution for identifying minor but specific N-glycans from complicated cellular samples, indicating the potential as a next-generation N-glycomics tool. Our novel approach for coupling LC and CE can also dramatically improve the sensitivity in other separation modes, which can be a new standard of 2D bioanalysis applicable not only to glycans, but also to other diverse biomolecules such as metabolites, proteins, and nucleic acids.

Development of a first-in-class antibody and a specific assay for α-1,6-fucosylated prostate-specific antigen

Prostate-specific antigen (PSA) levels are widely used to screen for prostate cancer, yet the test has poor sensitivity, specificity and predictive value, which leads to overdiagnosis and overtreatment. Alterations in the glycosylation status of PSA, including fucosylation, may offer scope for an improved biomarker. We sought to generate a monoclonal antibody (mAb) targeting α-1,6-fucosylated PSA (fuc-PSA) and to develop a tissue-based immunological assay for fuc-PSA detection. Immunogens representing fuc-PSA were used for immunisation and resultant mAbs were extensively characterised. The mAbs reacted specifically with fuc-PSA-specific glycopeptide, but not with aglycosylated PSA or glycan without the PSA peptide. Reactivity was confirmed using high-throughput surface plasmon resonance spectroscopy. X-ray crystallography investigations showed that the mAbs bound to an α-helical form of the peptide, whereas the native PSA epitope is linear. Protein unfolding was required for detection of fuc-PSA in patient samples. Peptide inhibition of fuc-PSA mAbs was observed with positive screening reagents, and target epitope specificity was observed in formalin-fixed, paraffin-embedded tissue samples. This research introduces a well-characterised, first-in-class antibody targeting fuc-PSA and presents the first crystal structure of an antibody demonstrating glycosylation-specific binding to a peptide.

The role of alpha-fetoprotein in the tumor microenvironment of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a prevalent malignant cancer worldwide, characterized by high morbidity and mortality rates. Alpha-fetoprotein (AFP) is a glycoprotein synthesized by the liver and yolk sac during fetal development. However, the serum levels of AFP exhibit a significant correlation with the onset and progression of HCC in adults. Extensive research has demonstrated that the tumor microenvironment (TME) plays a crucial role in the malignant transformation of HCC, and AFP is a key factor in the TME, promoting HCC development. The objective of this review was to analyze the existing knowledge regarding the role of AFP in the TME. Specifically, this review focused on the effect of AFP on various cells in the TME, tumor immune evasion, and clinical application of AFP in the diagnosis and treatment of HCC. These findings offer valuable insights into the clinical treatment of HCC.

Vesicular Integral-Membrane Protein 36 Is Involved in the Selective Secretion of Fucosylated Proteins into Bile Duct-like Structures in HepG2 Cells

Fucosylated proteins are widely used as biomarkers of cancer and inflammation. Fucosylated alpha-fetoprotein (AFP-L3) is a specific biomarker for hepatocellular carcinoma. We previously showed that increases in serum AFP-L3 levels depend on increased expression of fucosylation-regulatory genes and abnormal transport of fucosylated proteins in cancer cells. In normal hepatocytes, fucosylated proteins are selectively secreted in the bile duct but not blood. In cases of cancer cells without cellular polarity, this selective secretion system is destroyed. Here, we aimed to identify cargo proteins involved in the selective secretion of fucosylated proteins, such as AFP-L3, into bile duct-like structures in HepG2 hepatoma cells, which have cellular polarity like, in part, normal hepatocytes. α1-6 Fucosyltransferase (FUT8) is a key enzyme to synthesize core fucose and produce AFP-L3. Firstly, we knocked out the FUT8 gene in HepG2 cells and investigated the effects on the secretion of AFP-L3. AFP-L3 accumulated in bile duct-like structures in HepG2 cells, and this phenomenon was diminished by FUT8 knockout, suggesting that HepG2 cells have cargo proteins for AFP-L3. To identify cargo proteins involved in the secretion of fucosylated proteins in HepG2 cells, immunoprecipitation and the proteomic Strep-tag system experiments followed by mass spectrometry analyses were performed. As a result of proteomic analysis, seven kinds of lectin-like molecules were identified, and we selected vesicular integral membrane protein gene VIP36 as a candidate of the cargo protein that interacts with the α1-6 fucosylation (core fucose) on N-glycan according to bibliographical consideration. Expectedly, the knockout of the VIP36 gene in HepG2 cells suppressed the secretion of AFP-L3 and other fucosylated proteins, such as fucosylated alpha-1 antitrypsin, into bile duct-like structures. We propose that VIP36 could be a cargo protein involved in the apical secretion of fucosylated proteins in HepG2 cells.

The hidden potential of glycomarkers: Glycosylation studies in the service of cancer diagnosis and treatment

Changes in the glycosylation process appear early in carcinogenesis and evolve with the growth and spread of cancer. The correlation of the characteristic glycosylation signature with the tumor stage and the appropriate therapy choice is an important issue in translational medicine. Oncologists also pay attention to extracellular vesicles as reservoirs of new cancer glycomarkers that can be potent for cancer diagnosis/prognosis. In this review, we recall glycomarkers used in oncology and show their new glycoforms of improved clinical relevance. We summarize current knowledge on the biological functions of glycoepitopes in cancer-derived extracellular vesicles and their potential use in clinical practice. Is glycomics a future of cancer diagnosis? It may be, but in combination with other omics analyses than alone.

Mass Spectrometry-Based Glycoproteomic Workflows for Cancer Biomarker Discovery

Glycosylation has a clear role in cancer initiation and progression, with numerous studies identifying distinct glycan features or specific glycoproteoforms associated with cancer. Common findings include that aggressive cancers tend to have higher expression levels of enzymes that regulate glycosylation as well as glycoproteins with greater levels of complexity, increased branching, and enhanced chain length1. Research in cancer glycoproteomics over the last 50-plus years has mainly focused on technology development used to observe global changes in glycosylation. Efforts have also been made to connect glycans to their protein carriers as well as to delineate the role of these modifications in intracellular signaling and subsequent cell function. This review discusses currently available techniques utilizing mass spectrometry-based technologies used to study glycosylation and highlights areas for future advancement.

Construction and validation of a prognostic risk model for breast cancer based on protein expression

Breast cancer (BRCA) is the primary cause of mortality among females globally. The combination of advanced genomic analysis with proteomics characterization to construct a protein prognostic model will help to screen effective biomarkers and find new therapeutic directions. This study obtained proteomics data from The Cancer Proteome Atlas (TCPA) dataset and clinical data from The Cancer Genome Atlas (TCGA) dataset. Kaplan–Meier and Cox regression analyses were used to construct a prognostic risk model, which was consisted of 6 proteins (CASPASE7CLEAVEDD198, NFKBP65-pS536, PCADHERIN, P27, X4EBP1-pT70, and EIF4G). Based on risk curves, survival curves, receiver operating characteristic curves, and independent prognostic analysis, the protein prognostic model could be viewed as an independent factor to accurately predict the survival time of BRCA patients. We further validated that this prognostic model had good predictive performance in the GSE88770 dataset. The expression of 6 proteins was significantly associated with the overall survival of BRCA patients. The 6 proteins and encoding genes were differentially expressed in normal and primary tumor tissues and in different BRCA stages. In addition, we verified the expression of 3 differential proteins by immunohistochemistry and found that CDH3 and EIF4G1 were significantly higher in breast cancer tissues. Functional enrichment analysis indicated that the 6 genes were mainly related to the HIF-1 signaling pathway and the PI3K-AKT signaling pathway. This study suggested that the prognosis-related proteins might serve as new biomarkers for BRCA diagnosis, and that the risk model could be used to predict the prognosis of BRCA patients.

Development and Evaluation of a Robust Sandwich Immunoassay System Detecting Serum WFA-Reactive IgA1 for Diagnosis of IgA Nephropathy

Aberrant glycosylation of IgA1 is involved in the development of IgA nephropathy (IgAN). There are many reports of IgAN markers focusing on the glycoform of IgA1. None have been clinically applied as a routine test. In this study, we established an automated sandwich immunoassay system for detecting aberrant glycosylated IgA1, using Wisteria floribunda agglutinin (WFA) and anti-IgA1 monoclonal antibody. The diagnostic performance as an IgAN marker was evaluated. The usefulness of WFA for immunoassays was investigated by lectin microarray. A reliable standard for quantitative immunoassay measurements was designed by modifying a purified IgA1 substrate. A validation study using multiple serum specimens was performed using the established WFA-antibody sandwich automated immunoassay. Lectin microarray results showed that WFA specifically recognized N-glycans of agglutinated IgA1 in IgAN patients. The constructed IgA1 standard exhibited a wide dynamic range and high reactivity. In the validation study, serum WFA-reactive IgA1 (WFA+-IgA1) differed significantly between healthy control subjects and IgAN patients. The findings indicate that WFA is a suitable lectin that specifically targets abnormal agglutinated IgA1 in serum. We also describe an automated immunoassay system for detecting WFA+-IgA1, focusing on N-glycans.

High sensitivity silicon nanowire array sensor for joint detecting the tumor markers CEA and AFP

Liver cancer is one of the malignant tumors with the highest fatality rate and the increasing incidence, which has no effective treatment plan. Early diagnosis and early treatment of liver...

Integrated analysis of glycan and RNA in single cells

Single-cell sequencing has emerged as an indispensable technology to dissect cellular heterogeneity but never been applied to the simultaneous analysis of glycan and RNA. Using oligonucleotide-labeled lectins, we first established lectin-based glycan profiling of single cells by sequencing (scGlycan-seq). We then combined the scGlycan-seq with single-cell transcriptome profiling for joint analysis of glycan and RNA in single cells (scGR-seq). Using scGR-seq, we analyzed the two modalities in human induced pluripotent stem cells (hiPSCs) before and after differentiation into neural progenitor cells at the single-cell resolution. The combination of RNA and glycan separated the two cell types clearer than either one of them. Furthermore, integrative analysis of glycan and RNA modalities in single cells found known and unknown lectins that were specific to hiPSCs and coordinated with neural differentiation. Taken together, we demonstrate that scGR-seq can reveal the cellular heterogeneity and biological roles of glycans across multicellular systems.

Adult pancreatoblastoma: Current concepts in pathology

Adult pancreatoblastoma is an exceptionally rare malignant tumour of the pancreas that mimics other solid cellular neoplasms of the pancreas, which may pose diagnostic difficulties. Because of its rarity, little is known about its clinical and pathologic features. This article reviews the clinical and pathologic features of pancreatoblastoma in adults including differential diagnosis, treatment, and follow-up. Although pancreatoblastoma commonly occurs in childhood, there have now been more than 70 adult pancreatoblastomas described in the literature. There is a slight male predominance. There are no symptoms unique to pancreatoblastomas and adult patients are frequently symptomatic. The most common presenting symptom is abdominal pain. Grossly, the tumours are often large and well-circumscribed. Microscopically, pancreatoblastomas are composed of neoplastic cells with predominantly acinar differentiation and characteristic squamoid nests. These tumours are positive for trypsin, chymotrypsin, lipase, and BCL10. Loss of heterozygosity on chromosome 11p is the most common molecular alteration in pancreatoblastomas. Adult pancreatoblastomas are aggressive tumours with frequent local invasion, recurrence, and distant metastasis. Treatment consists of surgical resection. Chemotherapy and radiotherapy may have a role in the treatment of recurrent, residual, unresectable, and metastatic disease. It is important to distinguish pancreatoblastomas from morphological mimics such as acinar cell carcinomas, solid pseudopapillary neoplasms, and pancreatic neuroendocrine neoplasms.

Effectiveness of alpha-fetoprotein variants L2 and L3 as substitutes of alpha-fetoprotein in screening for fetal Trisomy 18

OBJECTIVE

To evaluate the effectiveness of alpha-fetoprotein variants (AFP-L2, AFP-L3) in fetal screening for Trisomy 18 in place of alpha fetoprotein (AFP).

METHODS

A retrospective case-control study was conducted. Collectively, 39 pregnant women bearing Trisomy 18 fetuses and 48 pregnant women with clinically normal and healthy fetuses were included. The serum AFP-L2 and AFP-L3 concentrations were detected by enzyme-linked immunosorbent assays. The likelihood ratio method and Python software were used to construct the risk model with AFP, free β-hCG, AFP-L2, and AFP-L3 to predict Trisomy 18. Receiver operating characteristic (ROC) curves were used to determine the optimal cutoff value, while the area under the curve (AUC) was used to assess the screening performance of AFP-L2 and AFP-L3 for fetal Trisomy 18.

RESULTS

Compared to values observed for the control group, AFP-L2 and AFP-L3 concentrations which were significantly higher (both p< .001) in pregnant women with Trisomy 18 fetuses were 7.95 ± 3.57 ng/mL and 2.53 ± 1.80 ng/mL, respectively. Comparisons across multiple modeling methods showed that the highest AUC of screened Trisomy 18 fetuses (0.992, 0.986, and 0.976) was yielded by AFP-L2 + AFP-L3 + free β-hCG, AFP-L2 + free β-hCG, and AFP-L3 + free β-hCG, with a sensitivity of 1.000 indicated in both instances. In different modeling methods, the order of AUC values was AFP-L2 + AFP-L3 + free β-hCG > AFP-L2 + free β-hCG > AFP-L3 + free β-hCG > AFP + free β-hCG.

CONCLUSIONS

AFP-L2 and AFP-L3 showed higher sensitivity and specificity as substitutes for AFP in screening Trisomy 18. These two markers indeed improved the screening efficiency and reduced the false positive rate, when compared with AFP only.

FUT8 Alpha-(1,6)-Fucosyltransferase in Cancer

Aberrant glycosylation is a universal feature of cancer cells that can impact all steps in tumour progression from malignant transformation to metastasis and immune evasion. One key change in tumour glycosylation is altered core fucosylation. Core fucosylation is driven by fucosyltransferase 8 (FUT8), which catalyses the addition of α1,6-fucose to the innermost GlcNAc residue of N-glycans. FUT8 is frequently upregulated in cancer, and plays a critical role in immune evasion, antibody-dependent cellular cytotoxicity (ADCC), and the regulation of TGF-β, EGF, α3β1 integrin and E-Cadherin. Here, we summarise the role of FUT8 in various cancers (including lung, liver, colorectal, ovarian, prostate, breast, melanoma, thyroid, and pancreatic), discuss the potential mechanisms involved, and outline opportunities to exploit FUT8 as a critical factor in cancer therapeutics in the future.

Glycan array analysis of Pholiota squarrosa lectin and other fucose-oriented lectins

The α(1,6)fucose residue attached to the N-glycoprotein core is suspected to play an essential role in the progression of several types of cancer. Lectins remain the first choice for probing glycan modifications, although they may lack specificity. Thus, efforts have been made to identify new lectins with a narrower core fucose (CF) detection profile. Here, we present a comparison of the classical Aleuria aurantia lectin (AAL), Lens culinaris agglutinin (LCA) and Aspergillus oryzae lectin (AOL) with the newer Pholiota squarrosa lectin (PhoSL), which has been described as being specific for core fucosylated N-glycans. To this end, we studied the binding profiles of the four lectins using mammalian glycan arrays from the Consortium of Functional Glycomics. To validate their glycan specificity, we probed AOL, LCA and PhoSL in western-blot assays using protein extracts from eight common colorectal cancer (CRC) lines and colorectal biopsies from a small cohort of patients with CRC. The results showed that (i) LCA and PhoSL were the most specific lectins for detecting the presence of CF in a concentration-dependent manner; (ii) PhoSL exhibited the highest N-glycan sequence restriction, with preferential binding to core fucosylated paucimannosidic-type N-glycans, (iii) the recognition ability of PhoSL was highly influenced by the presence of terminal N-acetyl-lactosamine; (iv) LCA bound to paucimannosidic, bi-antennary and tri-antennary core fucosylated N-glycans and (v) AOL and AAL exhibited broader specificity towards fucosylation. Together, our results support the choice of LCA as the most appropriate lectin for CF detection, as validated in protein extracts from CRC cell lines and tissue specimens from patients with CRC.

Monoclonal antibodies specific for podocalyxin expressed on human induced pluripotent stem cells

Human induced pluripotent stem cells (hiPSCs) are useful starting materials for the generation of cell therapy products, due to their pluripotency and ability to self-renew. Quality control of hiPSCs is extremely important in creating a stable supply of hPSC-derived products. Previously we identified an hiPSC-specific lectin probe, rBC2LCN, which binds specifically to α1,2-fucosylated glycan and recognizes podocalyxin (PODXL) as a glycoprotein ligand. In this study, we produced monoclonal antibodies (mAbs) specific for α1,2-fucosylated PODXL expressed on hiPSCs. PODXL was recombinantly expressed in fucosyltransferase 1 (FUT1)-transfected HEK293, followed by immunization into mice. Monoclonal antibodies, which bind to PODXL/FUT1-transfected cells, but not to cells transfected with only one of PODXL or FUT1, were screened by flow cytometry. The two mAbs generated (179-6B8C9 and 179-7E12E10), termed α1,2-fucosylated PODXL-specific mAbs (FpMabs), showed binding specificity to PODXL/FUT1-transfected cells. The FpMabs bound to hiPSCs but never to human adipose-derived mesenchymal stem cells, human dermal fibroblasts, or hiPSC-derived mesoderm. Altogether, FpMabs are highly specific probes for hiPSCs, which might be a powerful tool for the characterization of hiPSCs used in regenerative medicine.

Functional glycomics: Application to medical science and hepatology

Glycomics refers to the comprehensive analysis of glycans. Recent progress in glycotechnology enables the determination of a variety of biological functions of glycans. Among different glycosylation patterns, certain types of aberrant glycosylation are linked to cancer and/or inflammation, and thus have biological importance. Glycotechnology has been applied to many fields of medical science, including hepatology. In particular, dramatic changes in glycosylation are observed in the progression of liver diseases. As the liver produces so many serum glycoproteins, changes in glycosylation of these proteins might provide useful disease biomarkers. Furthermore, many patients with genetic diseases of glycosylation who have liver dysfunction have been found as a result from whole genome sequencing, and various kinds of glycotherapy have been developed, especially in immunotherapy. In this review, we describe our basic knowledge of glycobiology and discuss the application of these data to medical science, especially hepatology.